textproduct: Rapid City

KEY MESSAGES

- Upper ridge will dominate the weather through early next week - Thunderstorm chances will be very limited through Saturday afternoon - Temperatures will average about 4-8F above normal

DISCUSSION

(This Evening Through Wednesday) Issued at 1259 PM MDT Wed Aug 19 2026

18z surface analysis had a weak trough from eastern MT into western WY. 0.5km visible loop depicted a weak outflow boundary/CU over south-central SD in a regime characterized by little MLCIN per latest SPC mesoanalysis. Water vapour loop had upper ridge over the Rockies with northwest flow aloft over the northern Plains. A couple of weak wiggles noted, but nothing substantial.

Late this afternoon/evening, a stray shra/TS may develop over south-central SD along the boundary so have added 15% PoPs to account. Tonight into Thursday, aforementioned trough slips through the CWA with northwest winds behind it. Moisture is limited over the CWA, so don't expect any precipitation until the boundary exits the area and taps into better moisture over NE/southeast SD. These thoughts are in line with latest CAM guidance. Temperatures will be near guidance.

Friday through Saturday afternoon, upper ridge builds more strongly into the northern Plains with height rises generally suppressing convective chances, but wouldn't be surprised if something bubbles over the Black Hills during peak insolation. Saturday night through early next week, a series ridge-riders will bring periodic chances for tsra, but coverage will be hit-or-miss and many folks might not get anything. Temperatures a bit tricky per low confidence in cloud-cover/PoPs, but 4-8F above normal in- line with probabilistic guidance.

AVIATION

(For the 18Z TAFS Through 18Z Thursday) Issued At 1111 AM MDT Wed Aug 19 2026

VFR conditions are expected through the TAF period.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.